Several factors contribute to the slower acceleration observed in plug-in hybrid electric vehicles (PHEVs) when operating in electric vehicle (EV) mode:
- Increased Vehicle Weight: PHEVs are generally heavier than regular hybrids because they include both a combustion engine and a relatively large battery pack to enable electric-only driving. This additional weight adversely affects acceleration performance in EV mode since the electric motor alone must propel the heavier mass.
- Less Powerful Electric Motors Compared to Pure EVs: The electric motors in PHEVs tend to be less powerful than those found in fully electric vehicles (EVs). For example, Mercedes-Benz’s PHEV GLE450e has a 134-horsepower electric motor, whereas the fully electric EQE500 SUV from the same brand has a much stronger dual-motor electric powertrain delivering 402 horsepower. This lower electric motor output in PHEVs delays acceleration times significantly in EV mode versus hybrid or gas-assisted modes.
- Limited Power Delivery from Battery and Thermal Management Constraints: PHEVs have factory-set limits on EV mode top speeds and power output to protect the battery and electrical components from overheating and excessive wear. Higher power demands increase heat generation, so manufacturers cap maximum electric output and speed to maintain system reliability and safe operating temperatures. This results in more conservative acceleration capabilities in EV mode.
- Mode Prioritization and Engine Engagement at Higher Power Demands: PHEVs typically use the electric motor alone only under light throttle or low-speed conditions. When the driver demands rapid acceleration—such as flooring the accelerator or going uphill—the internal combustion engine (ICE) usually kicks in to provide additional power. This operational strategy prevents the electric motor from delivering sudden bursts of high power alone, causing slower acceleration in pure EV mode.
In real-world testing, these factors culminate in noticeably slower EV-only acceleration times for PHEVs. For instance, the Toyota Prius Prime took about twice as long to hit 60 mph in EV mode compared to hybrid mode, and the Mercedes-Benz GLE450e PHEV was nearly three times slower to 60 mph on electric power alone than with its gas engine assisting.
In summary, slower acceleration in EV mode for PHEVs mainly stems from their additional weight, relatively less powerful electric motors, manufacturer-imposed power limits to protect battery health, and the strategy to engage the combustion engine under higher acceleration demands. These combined influences distinguish PHEV EV-mode performance from that of full battery-electric vehicles.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/what-factors-contribute-to-the-slower-acceleration-in-ev-mode-for-phevs/
